Maximizing energy injections of distributed generation in rural areas

Since its introduction, distributed generation (DG) has surely allowed the exploitation of otherwise unrecoverable energy resources dispersed on the territory, though posing a series of as yet unsolved problems connected to smart grid operation. One of these inconveniences is the automatic DG disconnection in weak network. Actually, for a DG system to be able to inject power into a grid, the voltage value in its interconnection node must be increased. If voltage exceeds a certain limit, the current Protection System Interface (SPI) will disconnect the generator resulting in the total loss of the energy produced at that node. This paper proposes a number of solutions to the issue, making specific reference to inconveniences that actually occurred in DG systems installed in some Italian rural areas, but that might as well affect areas with higher load densities. During a first phase of the study, the current situations were analyzed and then a circuit model was implemented in a Matlab-Simulink environment to obtain an accurate system simulation. The DG taken into consideration mainly involved photovoltaic systems connected to LV networks, of different sizes and supposedly working in different operating conditions, depending on load demand and weather conditions. The results of the numerical simulation were properly illustrated and discussed, so as to establish the actual validity of the proposed solutions.